1. Field of the Invention
The present disclosure relates to the treatment of tissue damages. In particular, the disclosed invention relates to the use of PEDF-derived polypeptides for promoting muscle or tendon regeneration or arteriogenesis in the treatment of tissue damages.
2. Description of Related Art
Muscle tissues are classified as skeletal, cardiac or smooth muscles. Muscle is capable of repairing its damage. After injury, skeletal muscle is repaired by a spontaneous process to remove damaged myofibers and synthesizing new muscle fibers. However, such spontaneous tissue repair mechanism is absent in some tissue damage or inadequate to effect a full recovery of the tissue. For example, some pathologic conditions (such as severe injury, advanced age, muscle disuse, cancer, and tissue ischemia) or genetic defects (such as muscular dystrophy) may lead to impaired healing. Failure of repair may lead to permanent loss of muscle mass, disease progression, and functional deficiency.
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone. Tendon injuries generally result in inflammation and degeneration or weakening of the tendons, which may eventually lead to tendon rupture. Tendon healing is a long and intricate process that typically takes months, and over a time period of about one year, the tissue will gradually turn from fibrous to scar-like. Such scar tissue may result in reduced elasticity and mobility of the tendon and increased propensity for recurrence of injury. Tendon-derived stem cells (TSCs) and bone marrow-derived mesenchymal stem cells (BM-MSCs) offer limited autologous healing of tendonitis lesions.
Episodes of ischemia are another cause of considerable tissue damage. Ischemic episodes leading to tissue damage result in myocardial infarctions, stroke, and other disorders. Short episodes of ischemia cause mild damage from which a cell can recover, while longer periods of ischemia cause irreversible cell damage, leading to cell death. In the latter case, even if blood circulation is reestablished, total functional recovery of the damaged cell is impossible. Furthermore, loss of function always precedes cell death.
No present treatment for these conditions offers a cure or facilitates regeneration of the damaged, nonfunctional tissue. Thus, there exists a need in the art for means that promotes regeneration of tissue. In particular, it would be desirable to provide a composition and method for promoting arteriogenesis so as to promote blood flow in or adjacent to the damaged tissue region and to permit quasi-normal function to the tissue.